This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. PROJECT DESCRIPTION The epidermis is the principal interface between an animal and its environment. Development of the epidermis is dependent on a gene regulatory network that controls its differentiation and morphogenesis. Disruption of this regulatory network causes a number of human developmental and disease syndromes. This proposal aims at the dissection of the gene regulatory network for epidermal development in an emerging model organism, the ascidian Ciona intestinalis, taking the homeobox transcription factor gene DllB as a starting point. The research plan is to use transgenic reagents developed in our laboratory to alter expression of the pivotal regulator of epidermal cell specification CiDllB, and measure effects on the gene regulatory network for epidermal development. The specific aims are 1) measure changes in putative target gene expression levels in embryos altered by misexpression of CiDllB from ectodermal to endomesodermal cells;2) complete a CiDllB dominant negative transgene and examine the embryonic phenotype and effects on putative target gene expression levels;3) predict binding sites in previously cloned CiDllB regulatory elements and analyze upstream regulation by site-directed mutagenesis;4) develop methods for cleavage arrest and to separate ectodermal from endomesodermal cells by blastomere isolation in order to discover genes differentially expressed in the ectodermal lineage. These aims will allow us to work out and validate methods for gene regulatory network discovery applicable to proposals for larger projects which we are developing.